Semipermeable membranes may be used for a wide variety of separations involving liquid-liquid separations, liquid-liquid solid separations and gas-gas separations. The membranes which are employed for these purposes usually comprise various organic polymers or mixtures of organic polymers either alone or supported on a porous backing material. For example, semipermeable membranes which are used in desalination processes can comprise cellulose acetate polymers composited on a porous support which acts as a backing for the membrane, thin film composite membranes comprising polymeric compounds such as polyethyleneimine, epiamine, polyethylene, polypropylene films also composited on a porous support such as a polysulfone member, etc. Likewise, gaseous separation membranes may comprise polymeric membranes of cellulose nitrate or cellulose acetate support membranes having a polymer such as dimethylsilicone, styrene, silicon-carbide copolymers composited thereon, as well as thin film membranes such as polymethylpentene polymers. In addition to these membranes other permselective membranes such as heteropoly acids may be employed for separating gases such as hydrogen from mixtures of gases in a gaseous stream.
In a majority of cases, the admixture of an organic compound, especially in a polymeric state, with an inorganic compound, results in a phase separation, the two systems being immiscible in nature. However, we have now discovered that a polymer blended membrane may be fabricated by admixing a heteropoly acid or a salt thereof with an organic polymer which is at least partially compatible with said heteropoly acid or salt to form a polymer blended composition of matter which may be utilized as a membrane in a gas separation process. It was totally unexpected that a thin film membrane could be cast from such a blend to provide a membrane which would be highly selective to certain gases and therefore find a use in such separations involving a gas such as hydrogen.